The present invention relates to a digital tank circuit for use in such a circuit as a timing extractor for extracting timing information from an input signal.
A prior art digital tank circuit comprises sampling/converting means for sampling an analog signal at predetermined intervals of time and converting sampled values into corresponding predetermined binary codes, and a digital filter including adders, multipliers and delay elements. An example of such a digital filter is disclosed in a paper entitled "A New Hardware Realization of Digital Filters" by A. Peled and B. Liu, published in the IEEE Transactions ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING, ASSP-22 (6), pages 456 to 462, December 1974. Since the prior art filter requires at least four complicated multipliers, its manufacturing cost becomes high. Also, with respect to the gain characteristic of the digital filter to be used in the tank circuit, the sharper the peak at the center frequency, the more the influence of roundoff errors produced at the multipliers may not be considered negligible.
One object of the invention is, therefore, to provide a digital tank circuit without using multipliers free from the above-mentioned disadvantages in the prior art circuit.